As continuing refinements in micro-miniaturization techniques have increased the component occupancy densities of printed circuit boards, misalignment and imprecise shaping or formation of component leads have become significant concerns of system manufacturers, particularly those employing surface mount devices such as narrow pitch leaded chip carriers. Circuit components having high count, very narrow pitch leads are often processed using a tape automated bonding scheme, in which the part (the electronic circuit component) to be mounted on a circuit board is temporarily retained in a surrounding support frame or carrier. The extremely thin and narrow pitch leads of the part extend between the part and the frame and support tape is similarly employed to retain the part in the carrier during handling.
Because the retention carrier is relatively thin compared to its edgewise dimensions, it is customary to arrange a plurality of carriers in a stacked configuration. Individual carriers to be processed are separated off the top of the stack in a sideways direction, similar to dealing cards from the bottom of the deck. A separated carrier is then placed on a lead forming device, so that the part may be detached or excised from the carrier and the leads formed and trimmed for placement and attachment to a printed circuit board.
A fundamental problem to horizontal translation of a carrier from the top of the stack is the fact that the carrier surfaces are not perfectly smooth, so that the lowermost carrier may hang up on the next carrier, thereby hindering the feed and lead formation process. In addition, because `dealing` a carrier off the bottom of the stack involves horizontal or sideways movement (in a direction orthogonal to that of the stack) the feed mechanism requires a considerable hardware volume.